The present invention relates to a photocatalyst filter which uses a photocatalyst fiber of a light-leakage type and which will be called a light-leakage type photocatalyst filter hereinafter.
It is a recent trend that various problems have been presented about environmental pollution, such as air pollution. As regards the air pollution, it has been required for health to remove toxic substances, such as benzene, acetaldehyde, and the like from the air. To this end, various sorts of filters have been developed and sold but no proposals have been made yet which have sufficient characteristics.
The instant inventors have already proposed and filed a photocatalyst filter, namely, a photochemical catalysis filter which uses a bundle of photocatalyst fibers for removing the toxic substances from the air. With this structure, ultraviolet rays travel along the photocatalyst fibers and partially and gradually leak from the photocatalyst fibers to photochemically react with the toxic substances. Such photochemical reaction makes it possible to considerably remove the toxic substances, such as acetaldehyde. This type of the photocatalyst filter may be referred to as a light-leakage photocatalyst filter because light leakage is utilized in the photocatalyst filter.
More specifically, a light-leakage type photocatalyst filter proposed by the inventors comprises a bundle of photocatalyst fibers each of which has a fiber core portion formed by a photoconductor and a surface layer containing a photocatalyst, such as titanium oxide, and serving as a photocatalyst layer. The photocatalyst layer is activated by light or ultraviolet ray introduced into the fiber. The light travels along the photocatalyst fibers while partially leaking therefrom. Thus, the light-leakage type photocatalyst fiber exhibits a catalytic action. As mentioned before, the light-leakage type photocatalyst filter can be formed by bundling a plurality of light-leakage type photocatalyst fibers.
FIG. 1 shows an example of the light-leakage type photocatalytic filter.
Referring to FIG. 1, the light-leakage type photocatalyst filter generally comprises a light-leakage type photocatalyst fiber bundle 101, a casing 102, a light introducing window 103, and a light source 104.
The casing 102 is provided with an inflow port 121 and an outflow port 122 for an object fluid (for example, an air) to be processed, and has a structure such that the photocatalyst fiber bundle 101 is interposed between the inlet port 121 and the outlet port 122. The light introducing window 103 is formed at a part of the casing 102 to introduce the light from the light source 104 into the photocatalyst fiber bundle 101.
In the filter shown in FIG. 1, the object fluid passes through the filter across the light-leakage type photocatalyst fiber bundle 101. Thus, the object fluid is introduced into the casing 102 through the inflow port 121 and crosses the fiber bundle 101 during passage of the filter. During passage, the object fluid is filtered by both a mechanical filtering action of the fiber bundle 101 and a photochemical catalytic action of the photocatalyst fibers. As a result, the object substantially free from the toxic substance is discharged from the outflow port 122. However, it has been revealed by the present inventors that the conventional filter described above is disadvantageous in the following respects.
In the filter shown in FIG. 1, the object fluid crosses the photocatalyst fiber bundle 101 within the filter. It is therefore difficult to assure or lengthen a traveling distance (path length) within the filter, i.e., a so-called effective filter length. In addition, a passageway resistance across the fiber bundle 101 becomes undesirably large. This results in an increase of a pressure loss in the filter.
As a consequence, the efficiency of use of the photocatalyst fibers is low and thus a sufficient filtering capacity cannot be obtained as compared with the numbers of necessary photocatalyst fibers.
It is therefore an object of the present invention is to provide a light-leakage type photocatalyst filter capable of simultaneously satisfying contradictory demands for sufficiently lengthening an effective filter length, for reducing a pressure loss in the filter, and for increasing a filtering capacity by improving the efficiency of use of photocatalyst fibers.
According to a first aspect of this invention, there is provided a light-leakage type photocatalyst filter comprising a filter assembly including a plurality of photocatalyst fibers each of which is composed of a fiber-shaped base member of a photoconductor and a surface layer containing a photocatalyst and which are bundled together into a photocatalyst fiber bundle with a gap left between every adjacent ones of said photocatalyst fibers; light introducing means for introducing the light into each of said photocatalyst fibers forming the filter assembly; and fluid introducing means for introducing an object fluid to be processed into the filter assembly to make the fluid pass through the gap between the adjacent ones of the photocatalyst fibers in a longitudinal direction of the photocatalyst fibers.
According to a second aspect of this invention, the light-leakage type photocatalyst filter may have a reservoir formed in front of an end face of the filter assembly.
According to a third aspect of this invention, the photocatalyst fibers may be bundled together with granular spacers interposed between every adjacent ones of the fibers.
According to a fourth aspect of this invention, the filter assembly may be divided by a partition wall disposed along the longitudinal direction of the photocatalyst fibers to form a plurality of filter paths and to form a cascade channel in which the fluid object successively passes through the filter paths.
According to a fifth aspect of this invention, the photocatalyst fiber bundle may have a dense portion and a sparse portion formed at a part and another part in the longitudinal direction where the fibers are densely and sparsely arranged, respectively. The dense portion serves as the filter assembly while the sparse portion serves as a fluid introducing section communicating with an end face of the filter assembly.
According to a sixth aspect of this invention, the photocatalyst fiber bundle forming the filter assembly is arranged so that their end faces are inclined with respect to the longitudinal direction of the fiber bundle.
According to a seventh aspect of this invention, a traveling direction of the object fluid within the photocatalyst fiber bundle forming the filter assembly may be perpendicular to a light introducing direction of introducing the light into each photocatalyst fiber.
According to an eighth aspect of this invention, a traveling direction of the object fluid within the photocatalyst fiber bundle forming the filter assembly may be coincident with a light introducing direction of introducing the light into each photocatalyst fiber.
According to a ninth aspect of this invention, the light-leakage type photocatalyst filter may have a fluorescent surface formed on a light introduction end face of each of the photocatalyst fibers to perform secondary emission.
According to a tenth aspect of this invention, the light-leakage type photocatalyst filter may have an antireflection layer formed on an end face of each of the photocatalyst fibers on a light introduction end.
According to an eleventh aspect of this invention, there is provided a light-leakage type photoctalyst fileter comprising a filter assembly including a plurality of photocatalyst fibers each of which is composed of a fiber-shaped base member of a photoconductor and a surface layer containing a photocatalystand which are bundled together into a photocatalyst fiber bundle with a gap left between every adjacent ones of said photoctalyst fibers, a fluid inlet/outlet pipe having inflow and outflow ports for an object fluid containing an object material to be processed by the photocatalyst; and a light source for introducing the light into the photoconductor, wherein the filter assembly is disposed in the fluid inlet/outlet pipe so that a flowing direction of the object fluid is substantially coincident with a longitudinal direction of the fiber-shaped base members constituting the filter assembly while the light source is disposed so as to introduce the light into the fiber-shaped base members.
According to the present invention, the object fluid can be made to pass through the photocatalyst fiber bundle in the longitudinal direction thereof and the flow rate distribution of the object fluid can be uniformly distributed in the fiber bundle.
As a result, it is possible to achieve the object, i.e., to simultaneously satisfy the contradictory demands for assuring an effective filter length which is sufficiently long, for reducing a pressure loss in the filter, and for increasing a filter capacity by improving the efficiency of use of the photocatalyst fibers.